The present invention relates to a cutter for cutting structural members of buildings, vehicles, or ships and the like into pieces for demolition. More particularly, the present invention relates to a double scissors cutter for cutting thick sections of steel plate, beams and bars.
A heavy-duty shearing machine such as, for example, one disclosed in U.S. Pat. No. 5,146,683, includes a pair of linear scissors blades pivotable with respect to each other at a pivot. It is well known that scissors-type devices suffer from transverse spreading of the blades when cutting thick and tough material. For example, when a pair of household scissors is used in an attempt to cut a stack of papers which exceeds their capacity, or when the cutting edges of the scissors are insufficiently sharp to cut the stack of papers, the blades deflect transversely, with the stack of papers ending up, uncut, between the blades. The blade-spreading problem with household scissors is amplified vastly in an industrial environment where steel members such as, for example, steel plate of an inch or more in thickness, or I-beams up to 18 or 24 inches in cross section, must be cut. In ship demolition, combinations of plate and beams are encountered in no particular order or aspect. The '683 cutter accommodates the changing aspect of the material to be cut by employing a rotary joint for rotating the cutting plane of the cutter blades, and a two-axis articulating joint for varying the angle at which the cutter approaches the material to be cut.
The two-axis articulating joint is typically a conventional joint found at the end of a power shovel boom. The rotary joint of the '683 cutter is attached outboard of the articulating joint.
The problem of blade spreading is recognized in the '683 cutter. In its solution, the '683 patent employs a beak-like projection on a transversely thinner one of the cutting blades. When such a shearing machine is used to cut a structural member or workpiece having a length larger than that of its blades, it is difficult to completely cut such structural member along it entire length due to the interference between the blades and the structural member.
In order to avoid this problem, a double scissors cutter has been proposed which comprises a pair of jaw members having, in their abutting surface, a cutting blade of a substantially U-shaped configuration such being disclosed in Japanese Patent Publication No. 05(1993)3224. This cutter is capable of cutting a workpiece into small pieces of a rectangular configuration, so that the blades can be easily advanced. Further, such small pieces of a rectangular configuration have substantially constant dimensions and weight, so that they may be easily handled and recycled.
It is noted, however, that the above double scissors cutter has a problem in that rectangular cutout pieces may remain between the jaw members. Accordingly, such cutter requires sweeping operation to remove cutout pieces from the abutting surface of the jaw members after each cutting operation, since no discharge mechanism for such cutout pieces is provided. Such sweeping operation is performed, for example, by opening the jaw members after completion of cutting work, and by shaking the cutter. Such sweeping operation is of course time-consuming and burdensome.
A cutter provided with a discharge mechanism for cutout pieces has been proposed. The discharge mechanism includes a steel plate connected through springs to an abutting surface of one of the jaw members, the plate serving to displace cutout pieces outwardly from the jaw member. Specifically, the springs disposed between the plate and the one jaw member are compressed when the jaw members are closed. When the jaw members are opened, the thus compressed springs extend to urge the steel plate outwardly, so as to displace the remaining cutout pieces from the jaw member. It is to be noted that such discharge mechanism is undesirable since it makes the cutter construction complicated. It is also noted that, when the jaw members are engaged with each other, significant amount of force is applied therebetween, thus causing a risk of damage to the springs. Furthermore, a portion of the power applied to the jaw members is consumed to compress the springs, thus increasing power loss.